Here we go again . . . MK4

[routercnc]

Finished the 2nd pair off, cleaned up, holes drilled etc.


These are the corner pieces on the gantry-


Not that exciting so I thought I'd also post another way I just tried out of tapping the threads in those parts (well starting them at least) which is much quicker. I started with one of these tapping chucks from RDG tools - designed to either replace the drill press chuck or for use in the tailstock of a lathe. It has a tommy bar and the chuck is free to rotate and slide inside the morse taper housing:


Link below (they are also on e-bay)
http://www.rdgtools.co.uk/acatalog/2...ent-88025.html

Although you are supposed to tap out the existing chuck and replace it with this one I didn't want to keep swapping them over. I'd looked these over at a show so knew that the MT3 taper comes off the chuck leaving a 12mm straight rod - perfect :


Because the 12mm rod was greased I put it inside a plastic bag (to stop the grease going onto the chuck jaws) and then put in lightly in the chuck - just enough to hold it but still allow it to rotate and slide up and down:


Here it is well into tapping the M5 thread:

This takes seconds to do and you can feel the bite / back off and reduce the risk of breaking the tap.

Note that the drill press is NOT powered - I'm using the tommy bar to rotate it manually.

This worked really well, was very quick, and created threads which were perpendicular to the face. I finished them off by putting the parts in a vice and using a cordless drill.

I think the plastic will not last long, it started has started to tear already, so one option is to make a metal adapter tube which is clamped in the drill press chuck at the top, and contains a long bored out 12.05mm dia or so hole in the bottom to hold the greased rod on the end of the tapping chuck. If the bore is a good fit and there is grease in there it should stop the chuck falling out when you raise the drill press.

To have something set up permanently I might even modify a cheap drill press/stand (the ones where you put a mains drill in) to house a long rod attached to the drill chuck - a bit like the Arc Euro ones but their's only goes to about 6mm or so tap size whereas this goes to 13mm.

[Neale]

I cheated a couple of days ago when I needed to tap some M8 holes in a slab of Ecocast I had just drilled. I held the M8 spiral-point tap directly in the drill chuck, and took off the drive belt on the mill (Warco VMC with multi-speed belt drive so easy to do). I could then turn the drive pulley by hand. Light down pressure on downfeed handle, and this was enough to get a good thread started, finished by hand later. For small taps, I have lightly guided them in the chuck jaws and tightened a tap wrench on to the shank (not square) of the tap to turn them. Especially with these easily-driven spiral-point taps, this works ok to get a thread started. But I'll have to have a look at the RDG tap holder the next time I see them at an exhibition - thanks.

[routercnc]

Hi Neale,

Yes, done something similar to that by slackening the motor / belt tension levers on the drill press. But even with the belt slack there is still quite alot of friction and it still tries to turn the motor.

To remove the belt on my Warco pillar drill completely takes a bit of time and involves a ladder, a screwdriver to open the lid, and releasing the motor bolts and is not very efficient. It's not much fun for long due to the effort of turning the chuck & motor.

The method above is quick to set up (just a quick adjustment on the chuck jaws) and is then very easy to turn.

One thing I will note is that the tap slipped occasionally, even though I tightened it as much as I could. I don't know if they do a keyed chuck version but that might be better. Maybe a bit of degrease on the inside of the chuck jaws would help. Next time I'll also try a tap handle on the round part of the tap shank as you did.

[routercnc]

Bit more progress. One of the gantry end plates was cut out over the weekend:


Tonight I drilled and tapped all the various holes. Couldn't resist a trial fit of a couple of the previous parts:
OUTER VIEW

(Note the tabs on each end still need facing off. I'll wait for the other one to be machined then do them in the same session.)

INNER VIEW


With the side plates offered up:






Another reminder of what the end sections should look like . ..



I used the tapping chuck again which made light work of the threads. Also discovered I was holding the tap wrong. I had been putting the tap right into the chuck and it gripped on the round shank - liable to slip. Looking at the 3 jaws of the chuck I noticed that it has ridges in the centre of each jaw. If you put the square part of the tap into the chuck these grip the 4 sides nicely, with 2 jaws on the flats and 1 jaw (with the ridge) on one of the chamfers of the square. Hard to describe but just put the square shank of the tap into the 3 jaw chuck and it will not rotate.